<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title></title>
    </head>
    <body>
        <button onclick="start()">111</button>
        <script>
            window.onload = function() {    
                function start() {
                    alert('111');
                }
            }    
        </script>
    </body>
</html>